1643 has 4 divisors (see below), whose sum is σ = 1728. Its totient is φ = 1560.

The previous prime is 1637. The next prime is 1657. The reversal of 1643 is 3461.

1643 is nontrivially palindromic in base 12.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1643 - 2^{4} = 1627 is a prime.

It is an Ulam number.

It is a Duffinian number.

1643 is an undulating number in base 12.

It is a plaindrome in base 6, base 9 and base 16.

It is a nialpdrome in base 13 and base 14.

It is an inconsummate number, since it does not exist a number *n* which divided by its sum of digits gives 1643.

It is not an unprimeable number, because it can be changed into a prime (1613) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5 + ... + 57.

It is an arithmetic number, because the mean of its divisors is an integer number (432).

1643 is a deficient number, since it is larger than the sum of its proper divisors (85).

1643 is an equidigital number, since it uses as much as digits as its factorization.

1643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 84.

The product of its digits is 72, while the sum is 14.

The square root of 1643 is about 40.5339363990. The cubic root of 1643 is about 11.7999233932.

The spelling of 1643 in words is "one thousand, six hundred forty-three".

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